Duodenal Strongyloidiasis Mimicking Inflammatory Bowel Disease: A Case Report of a 52-Year-Old Immunocompetent Woman.

Abstract

Background: Strongyloides stercoralis is an intestinal nematode with a unique autoinfective life cycle that enables decades-long persistence in the human host. Its gastrointestinal manifestations may resemble inflammatory bowel disease (IBD), creating a clinically important diagnostic pitfall. Misdiagnosis is particularly hazardous because corticosteroids or other immunosuppressive therapies may precipitate Strongyloides hyperinfection syndrome or disseminated disease.

Case presentation: We report a 52-year-old immunocompetent woman from northern Iran who presented with a 20-day history of persistent watery inflammatory diarrhea, severe hypokalemia (2.4 mEq/L), leukocytosis, and thrombocytosis. Serial stool examinations for ova and parasites were repeatedly negative for larvae; however, fecal leukocytes and erythrocytes, together with erosive duodenopathy, initially raised concern for IBD. Duodenal biopsy established the diagnosis by demonstrating marked eosinophilic infiltration of the lamina propria, reaching 45-50 eosinophils per high-power field, and rhabditiform larvae within the mucosal crypts. The larvae showed morphologic features supporting Strongyloides stercoralis, including a short buccal cavity/canal and a characteristic rhabditiform esophagus. Molecular testing, serology, and independent expert parasitologist confirmation were not performed, which represents a diagnostic limitation. The patient was treated with oral ivermectin plus adjunctive albendazole. The addition of albendazole was an individualized, non-standard clinical decision rather than a routine evidence-based recommendation. Her symptoms improved rapidly, and she remained asymptomatic at one-month follow-up.

Conclusion: This case emphasizes the clinical and histopathological overlap between duodenal strongyloidiasis and IBD, particularly when stool parasitology is unrevealing. The novelty of this report lies primarily in its didactic value for clinicians in endemic regions: Strongyloides should remain in the differential diagnosis of IBD-like presentations with unexplained eosinophilic mucosal inflammation before immunosuppressive therapy is considered.